Novel photographic products and processes

ABSTRACT

Novel photograhpic products for use in diffusion transfer systems for forming visible images, particularly systems for forming color images viewable, without separation as color reflection prints, which products include a neutralizing layer for lowering the environmental pH after application of an aqueous alkaline processing fluid, the neutralizing layer being prepared by coating an aqueous solution of a water-soluble cross-linkable acidic polymer on a layer of the film unit including a nondiffusible cross-linking agent for the acidic polymer, whereby to cross-link and thereby harden the thus applied layer of acidic polymer at least at the interface of the respective layers. The non-diffusible cross-linking agent may be the only component of the layer or substrate on which the neutralizing layer is applied or it may be present along with other materials, e.g., as the major component of the substrate.

United States Patent [191 Haas [ Sept. 3, 1974 NOVEL PHOTOGRAPHIC PRODUCTS AND PROCESSES [75] Inventor: Howard C. Haas, Arlington, Mass.

[73] Assignee: Polaroid Corporation, Cambridge,

Mass.

[22] Filed: May 3, 1972 [2]] Appl. No.: 249,849

Primary ExaminerRonald H. Smith Assistant ExaminerRichard L. Schilling Attorney, Agent, or Firm-Alvin lsaacs; John P. Morley 5 7 ABSTRACT Novel photograhpic products for use in diffusion transfer systems for forming visible images, particularly systems for forming color images viewable, without separation as color reflection prints, which products include a neutralizing layer for lowering the environmental pH after application of an aqueous alkaline processing fluid, the neutralizing layer being prepared by coating an aqueous solution of a water-soluble cross-linkable acidic polymer on a layer of the film unit including a non-diffusible cross-linking agent for the acidic polymer, whereby to cross-link and thereby harden the thus applied layer of acidic polymer at least at the interface of the respective layers. The nondiffusible cross-linking agent may be the only component of the layer or substrate on which the neutralizing layer is applied or it may be present along with other materials, e.g., as the major component of the substrate.

30 Claims, 1 Drawing Figure SUPPORT CYAN DYE DEVELOPER LAYER RED-SENSITNE SILVER HALIDE LAYER LAYER DYE DEVELOPER LAYER GREEN-SENSITIVE SILVER HALIDE LAYER YER DYE DEVELOPER LAYER SENSIT|VE SILVER HALIDE LAYER LIARY LAYER -RECEIVING LAYER LAYER LAYER PATENTED 3E? l974 SUPPORT -CYAN DYE DEVELOPER LAYER REDSENSITIVE SILVER HALIDE EMULSION LAYER INTER LAYER MAGENTA DYE DEVELOPER LAYER GREEN-SENSITIVE SILVER HAUDE EMULSION LAYER -INTER LAYER NJYELLOW DYE DEVELOPER LAYER BLUE-SENSILIVE SILVER HALIDE EMULSION LAYER L/AUXILIARY LAYER -IMAGE-RECEIVING LAYER fsPACER LAYER NEUTRALlZING LAYER SUPP T I /f NOVEL PI-IOTOGRAPHIC PRODUCTS AND PROCESSES BACKGROUND OF THE INVENTION Various diffusion transfer systems for forming color images have heretofore been disclosed in the art. Generally speaking, such systems rely for color image formation upon a differential in mobility or solubility of a dye image-providing material obtained as a function of development so as to provide an imagewise distribution of such material which is more diffusible and which is therefore selectively transferred, at least in part, by diffusion, to a superposed dyeable stratum to impart thereto the desired color transfer image. The differential in mobility or solubility may for example be obtained by a chemical action such as a redox reaction or a coupling reaction.

The dye image-providing materials which may be employed in such processes generally may be characterized as either I) initially soluble or diffusible in the processing composition but are selectively rendered nondiffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.

As examples of initially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in U.S. Pat. Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in US. Pat. Nos. 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294 and 3,445,228.

In any of these systems, multicolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripack structures employing a blue-, a greenand a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan dye image-providing material.

A particularly useful system for forming color images by diffusion transfer is that described in US. Pat. No. 2,983,606, employing dye developers (dyes which are also silver halide developing agents) as the dye imageproviding materials. In such systems, a photosensitive element comprising at least one silver halide layer having a dye developer associated therewith (in the same or in an adjacent layer) is developed by applying an aqueous alkaline processing composition. Exposed and developable silver halide is developed by the dye developer which in turn becomes oxidized to provide an oxidation product which is appreciably less diffusible than the unreacted dye developer, thereby providing an imagewise distribution of diffusible dye developer in terms of unexposed areas of the silver halide layer, which imagewise distribution is then transferred, at least in part, by diffusion, to a dyeable stratum to impart thereto a positive dye transfer image. Multicolor images may be obtained with a photosensitive element having two or more selectively sensitized silver halide layers and associated dye developers, a tripack structure of the type described above and in various patents including the aforementioned US. Pat. No. 2,983,606 being especially suitable for accurate color recordation of the original subject matter.

In color diffusion transfer systems of the foregoing description, color images are obtained by exposing a photosensitive element or negative component comprising at least a light-sensitive layer, e.g., a gelatino silver halide emulsion layer, having a dye imageproviding material associated therewith in the same or in an adjacent layer, to form a developable image; developing this exposed element with a processing composition to form an imagewise distribution of a soluble and diffusible image-providing material; and transferring this imagewise distribution, at least in part, by diffusion, to a superposed receiving element or positive component comprising at least a dyeable stratum to impart to this stratum a color transfer image. The negative and positive components may be separate elements which are brought together during processing and thereafter either retained together as the final print or separated following image formation; or they may together comprise a unitary structure, e.g., integral negative-positive film units wherein the negative and positive components are laminated and/or otherwise physically retained together at least prior to image formation.

While the present invention is applicable both to those systems wherein the dyeable stratum is contained on a separate element and to those systems wherein the dyeable stratum and the photosensitive strata comprise a unitary structure, of particular interest are those integral negativepositive film units adapted for forming color transfer images viewable without separation, i.e., wherein the positive component need not be separated from the negative component for viewing purposes. Generally, such film units comprise a plurality of essential layers including a negative component comprising at least one light-sensitive silver halide and associated dye image-providing material and a positive component comprising dyeable stratum. These components may be laminated together or otherwise secured together in physical juxtaposition as a single structure. Film units intended to provide multicolor images comprise two or more selectively sensitized silver halide layers each having associated therewith an appropriate dye image-providing material exhibiting desired spectral absorption characteristics. As was heretofore mentioned the most commonly employed negative components for forming multicolor images are of the tripack structure containing a blue-, a greenand a redsensitive silver halide layer having associated therewith in the same or in a contiguous layer a yellow, a magenta and a cyan dye image-providing material respectively. Interlayers or spacer layers may if desired be provided between the respective silver halide layers and associated dye imageproviding materials. In addition to the aforementioned essential layers, such film units further include means for providing a reflecting layer between tum, without separation, by reflected light. This reflecting layer may comprise a preformed layer of a reflecting agent included in the essential layers of the film unit or the reflecting agent may be provided after photoexposure, e.g., by including the reflecting agent in the processing composition. These essential layers are preferably contained on a transparent dimensionally stable layer or support member positioned closest to the dyeable stratum so that the resulting transfer image is viewable through this transparent layer. Most preferably another dimensionally stable layer which may be transparent or opaque is positioned on the opposed surface of the essential layers so that the aforementioned essential layers are sandwiched or confined between a pair of dimensionally stable layers or support members, at least one of which is transparent to permit viewing therethrough of a color transfer image obtained as a function of development of the exposed film unit in accordance with the known color diffusion transfer system such as will be detailed hereinafter. In a particularly preferred form such film units are employed in conjunction with a rupturable container of known description containing the requisite processing composition and adapted upon application of pressure of applying its contents to develop the exposed film unit, e.g., by applying the processing composition in a substantially uniform layer between the dyeable stratum and the negative component. It will be appreciated that the film unit may optionally contain other layers performing specific desired functions, e.g., spacer layers, etc.

Opacifying means may be provided on either side of the negative component so that the film unit may be processed in the light to provide the desired color transfer image. In a particularly useful embodiment such opacifying means comprise an opaque dimensionally stable layer or support member positioned on the free or outer surface of the negative component, i.e., on the surface of the film unit opposed from the positive component containing the dyeable stratum to prevent photoexposure by actinic light incident thereon from this side of the film unit and an opacifying agent applied during development between the dyeable stratum and the negative component, e.g., by including the opacifying agent in a developing composition so applied, in order to prevent further exposure (fogging) by actinic light incident thereon from the other side of the film unit when the thus exposed film unit is developed in the light. The last-mentioned opacifying agent may comprise the aforementioned reflecting agent which masks the negative component and provides the requisite background for viewing the transfer image formed thereover. Where this reflecting agent does not by itself provide the requisite opacity it may be employed in combination with an additional opacifying agent in order to prevent further exposure of the lightsensitive silver halide layer or layers by actinic light incident thereon.

As examples of such integral negative-positive film units for preparing color transfer images viewable without separation as reflection prints, mention may be made of those described and claimed in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646; 3,473,925; 3,573,043; 3,576,625; 3,573,042; 3,594,164; and 3,594,165.

In general, the integral negative-positive film units of the foregoing description, e.g., those described in the aforementioned patents, are exposed to form a developable image and thereafter developed by applying the appropriate processing composition to develop exposed silver halide and to form, as a function of development, an imagewise distribution of diffusible dye image-providing material which is transferred, at least in part by diffusion, to the dyeable stratum to impart thereto the desired color transfer image, e.g., a positive color transfer image. Common to all of these systems is the provision of a reflecting layer between the dyeable stratum and the photosensitive strata to mask effectively the latter and to provide a background for viewing the color image contained in the dyeable stratum, whereby this image is viewable without separation, from the other layers or elements of the film unit. In certain of these systems, this reflecting layer is provided prior to photoexposure, e. g., as a preformed layer included in the essential layers of the laminar structure comprising the film unit, and in others it is provided at some time thereafter, e. g., by including a suitable lightreflecting agent, for example, a white pigment such as titanium dioxide, in the processing composition which is applied between the dyeable stratum and the next adjacent layer to develop the latent image and to form the color transfer image.

The dye image-providing materials which may be employed in such processes generally are selected from those materials heretofore mentioned and disclosed in the illustrative patents which were initially soluble or diffusible in the processing composition but which are selectively rendered non-diffusible as a function of development or those which are initially insoluble or nondiffusible in the processing composition but are selectively rendered diffusible as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.

A preferred opacification system to be contained in the processing composition is that described in the copending applications of Edwin H. Land, Serial No. 43,782, filed June 5, 1970, and now abandoned and Serial No. 101,968, filed December 28, 1970, now U.S. Pat. No. 3,647,437, comprising an inorganic reflecting pigment dispersion containing at least one optical filter agent at a pH above the pKa of the optical filter agent in a concentration effective, when the processing composition is applied, to provide a layer exhibiting optical transmission density than about 6.0 density units with respect to incident radiation actinic to the photosensitive silver halide layer and optical reflection density than about 1.0 density with respect to incident visible radiation.

In lieu of having the reflecting pigment contained in the processing composition, e.g., as disclosed in the aforementioned copending applications, the reflecting pigment needed to mask the photosensitive strata and to provide the requisite background for viewing the color transfer image formed in the receiving layer may be contained initially in whole or in part as a preformed layer in the film unit. As an example of such a preformed layer, mention may be made of that disclosed on the copending applications of Edwin H. Land, Ser. Nos. 846,441, filed July 31, 1969, now U.S. Pat. No. 3,615,421, and 3,645, filed Jan. 19, 1970, now U.S. Pat. No. 3,620,724. The reflecting pigment may be generated in situ as is disclosed in the copending applications of Edwin H. Land, Ser. Nos. 43,741 and 43,742, both filed June 5, 1970, now U.S. Pat. Nos. 3,647,434 and 3,647,435, respectively.

In the various color diffusion transfer systems which have previously been described and which employ an aqueous alkaline processing fluid, it is well known to employ an acid-containing layer to lower the environmental pH following substantial dye transfer in order to increase the image stability and/or to adjust the pH from a first pH at which the imaging dyes are diffusible to a second (lower) pH at which they are not. For example, U.S. Pat. No. 3,362,819 discloses systems wherein the desired pH reduction may be effected by providing a polymeric acid layer adjacent the dyeable stratum. These polymeric acids may be polymers which contain acid groups, e.g., carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals or with organic bases; or potentially acidyielding groups such as anhydrides or lactones. Preferably the acid polymer contains free carboxyl groups. As examples of other useful neutralizing layers, in addition to those disclosed in the aforementioned U.S. Pat. No. 3,362,819, mention may be made of those disclosed in the following copending applications: Ser. No. 165,171 of Schlein et al., filed July 22, 1971; Ser. No. 214,746 of Bedell, filed Jan. 3, 1972; Ser. No. 208,616 of Taylor, filed Dec. 16, 1971; Ser. No. 231,835 of Sahatjian et al., filed Mar. 6, 1972, etc.

An inert interlayer or spacer layer may be and is preferably disposed between the polymeric acid layer and the dyeable stratum in order to control the pH reduction so that it is not premature and hence interferes with the development process, e.g., to time control the pH reduction. Suitable spacer or timer layers for this purpose are described with particularity in U.S. Pat. No. 3,362,819 and in others, including U.S. Pat. Nos. 3,419,389; 3,421,893; 3,433,633; 3,455,686; and 3,575,701.

While the acid layer and associated spacer layer are preferably contained in the receiving element employed in systems wherein the dyeable stratum and photosensitive strata are contained on separate elements, e.g., between the support for the receiving element and the dyeable stratum; or associated with the dyeable stratum in those integral film units, e.g., on the side of the dyeable stratum opposed from the negative component, they may, if desired, be associated with the photosensitive strata, as is disclosed, for example, in U.S. Pat. Nos. 3,362,821 and 3,573,043. In film units such as those described in the aforementioned U.S. Pat. Nos. 3,594,164 and 3,594,165, they also may be contained on the spreader sheet employed to facilitate application of the processing fluid.

The present invention is directed to a novel neutralizing layer for lowering the environmental pH in color diffusion transfer systems of the type previously described, which layer provides the distinct advantages and beneficial results which will be described hereinafter in the detailed description of the invention.

SUMMARY OF THE INVENTION In accordance with the present invention, the underlying layer of the photographic product on which the neutralizing layer is applied includes a non-diffusible cross-linking agent and the coating solution employed to provide the neutralizing layer comprises an aqueous solution of a water-soluble cross-linkable acidic polymer which is adapted to be crosslinked and thus hardened by the cross-linking agent of the underlying layer or substrate to which the aqueous coating solution is applied, at least at the interface between this substrate and the thus applied neutralizing layer, thereby providing increased resistance against possible subsequent delamination at this interface. The cross-linking agent may be the only or essential ingredient of this underlying layer or it may be contained along with other components together forming this underlying layer. Where found desirable or expedient to do so, the coating solution employed to form the neutralizing layer may also contain the same or a different cross-linking agent. However, the presence of this additional cross-linking agent in the coating solution is not essential to the practice of this invention.

BRIEF DESCRIPTION OF DRAWING The FIGURE is an enlarged, fragmentary, diagrammatic, sectional view of a film unit contemplated by this invention.

DESCRIPTION OF PREFERRED EMBODIMENT In the preferred embodiment, the film unit is an integral negative-positive film unit and the positive component includes the neutralizing layer in addition to the dyeable stratum. Most preferably, the substrate or underlying layer on which the neutralizing layer is applied comprises a sub-coating of a suitable cross-linking agent such as gelatin or the like on a transparent support through which the resulting color image is to be viewed and the cross-linkable acidic polymer in the aqueous coating solution employed to prepare the neutralizing layer comprises a copolymer of a vinyl acid and a vinyl aldehyde.

As was mentioned previously, the present invention contemplates photographic products including a neutralizing layer for lowering the environmental pH and which is prepared by coating an aqueous solution of a water-soluble cross-linkable acidic polymer on a substrate or underlying layer of the photographic product which includes or comprises a non-diffusible crosslinking agent so that following application of the aqueous coating cross-linking and subsequent hardening of the acidic polymer occurs, at least at the interface, to provide increased adhesion or resistance against delamination subsequent to application of an aqueous processing fluid to form the color transfer image. The present invention is useful in systems wherein the photosensitive strata and the dyeable stratum are contained on separate elements; and in systems wherein they are contained together as a unitary film unit, e.g., in the integral negative-positive film units previously described. In the former type, the neutralizing layer is most preferably contained in association with the dyeable stratum, e.g., in an image-receiving element comprising a support carrying the neutralizing layer and the dyeable stratum, a timing or spacer layer preferably being disposed therebetween. It may however becontained in the photosensitive element, i.e., in the element containing the photosensitive strata, as is disclosed in U.S. Pat. No. 3,362,821, or associated with a spreader sheet or separate sheet-like element employed to facilitate application of the processing fluid in those systems wherein the processing fluid is applied on the surface of the film unit rather than between layers of the film unit and a spreader sheet or the like is employed to facilitate this application of the processing fluid to the surface of the exposed film unit. In like manner, in the integral negative-positive film units, the

neutralizing layer is preferably associated with the dyeable stratum, e.g., on the side of the dyeable stratum opposed from the negative component. Again, a timing layer may be, and preferably is disposed between the dyeable stratum and neutralizing layer to perform its known function of time controlling diffusion of the processing fluid to the neutralizing layer and subsequent pH reduction.

In any of these systems, it will be appreciated that it is advantageous wherever applicable that the neutralizing layer, as well as the other layers of the product, be prepared from aqueous coating solutions, thereby obviating the need for organic solvents and the obvious manufacturing disadvantages inherent in the use of organic coating solutions, e. g., the need for special equipment to handle these solvents which are typically volatile, including the storage thereof before use, solvent recovery or recycling, and the involved danger in the use of such solvents, as well as possible contamination due to the presence of trace amounts of these solvents.

For these reasons, it is desirable to employ aqueous solutions of water-soluble or hydrophilic acids to prepare the neutralizing layer. However, with the use of such hydrophilic acids, there is the inherent problem of water from the processing fluid piling up at the neutralizing layer, which in turn causes certain distinct problems, chief of which is the tendency for delamination to occur. This separation of course renders the final print objectionable. While this problem is most pronounced in those film units wherein the negative and positive components are retained together at least after image formation so that the processing fluid remains confined therebetween, e.g., in the aforementioned integral film units, it is also a problem, although to a lesser extent, in those systems wherein the respective negative and positive components are retained on separate elements which are separated following image formation.

The present invention is directed to this problem and, in particular, to the concept of preparing the neutralizing layer from aqueous coating media, to achieve the advantages resulting from the use of such media; while at the same time obviating the disadvantages which may result from the use of hydrophilic acids, e.g., the aforementioned problems of delamination.

In accordance with the present invention, the acidic material is coated from an aqueous solution and subsequent to coating the acidic material is hardened by a cross-linking action per se well known in polymer chemistry into a more durable, less water soluble or hydrophobic acidic material.

The acidic polymers employed in the practice of this invention are selected from those which are watersoluble, cross-linkable and which, of course, contain acid groups, e.g., carboxylic acid or sulfonic acid groups, which are capable of forming salts with alkali metals or with organic bases; or potentially acidyielding groups such as anhydrides or lactones. Preferably the acidic polymer contains free carboxyl groups.

A preferred class of useful acidic polymers of this description are copolymers of vinyl acids and vinyl aldehydes. As examples of vinyl aldehydes which may be used in preparing such acids, mention may be made of acrolein (propenal) and homologues and analogues thereof, e. g., crotonaldehyde (2-butenal), tiglaldehyde (2-methyl-2-butenal), cinnamaldehyde (3-phenylpropenal), etc. Preferred vinyl acids are acrylic acid, its homologues and anlogues, e.g., methacrylic acid (propenoic acid), methacrylic acid, senecioic acid (B,B-dimethylacrylic acid), etc.

Polymers of the aforementioned acids and aldehydes may be referred to as vinyl polymers containing carboxylic groups, e.g., as polymers of acrolein containing carboxylic groups. Such polymers are per se old and are disclosed, for example, in US. Pat. No. 3,396,029. As is disclosed in that patent, such polymers may be prepared by the Cannizzaro reaction. It also disclosed in that patent that these polymers are useful as hardening agents for proteinaceous materials such as gelatin. In accordance with the teachings of the patent, the polymeric acid is included in the proteinaceous coating composition in an amount on the order of 0.5 to 4 percent by weight based on the dry proteinaceous material in order to obtain the desired hardening. Thus, a small amount of the polymeric acid hardener is included in the coating composition according to the patent in order to obtain the desired hardened proteinaceous layer.

The preferred embodiment of this invention employs similar polymeric acids and relies upon a similar chemical action to accomplish the objectives of this invention. Specifically, when an aqueous coating composition containing the polymeric acid is applied to a substrate comprising or including a proteinaceous material, e.g., gelatin, casein, etc., this proteinaceous material serves as a cross-linking agent to harden the polymeric acid, at least at the interface between the respective layers. It will thus be seen that whereas the preferred embodiment of the present application and the aforementioned patent rely upon a similar reaction between polymeric acid and proteinaceous material, the two are quite dissimilar in objectives as well as in the physical structures of the contemplated products.

In general, the vinyl acid moiety in the preferred acid polymers of this invention will be appreciably greater than the aldehyde moiety. For example, the ratio of vinyl acid to vinyl aldehyde may be on the order of at least :15. A preferred polymer of this description comprises a copolymer of acrylic acid and acrolein, the ratio of acrylic acid to acrolein being on the order of :10.

Where found desirable or expedient to do so, it is contemplated that small amounts of gelatin or other crosslinking agents may be included along with the polymeric acid in the aqueous coating composition employed to prepare the neutralizing layer.

As was heretofore mentioned, the neutralizing layer of this invention is useful in systems wherein the photosensitive strata and the dyeable stratum are contained on separate elements; and in systems wherein they are contained together as a unitary film unit, e. g., in the integral negative-positive film units previously described. In the former type, the neutralizing layer is most preferably contained in association with the dyeable stratum, e.g., in an image-receiving element comprising a support carrying the neutralizing layer and the dyeable stratum, a spacer or timing" layer preferably being disposed therebetween. It may however be contained as a layer in the photosensitive element, i.e., in the element containing the photosensitive strata, as is disclosed in US. Pat. No. 3,362,821. In like manner, in the integral negative-positive film units, the neutralizing layer is preferably associated with the dyeable stratum, e.g., on the side of the dyeable stratum opposed from the negative component, and most preferably a timing layer is disposed between the neutralizing layer and dyeable stratum.

Of particular interest are those film units such as the heretofore described integral negative-positive film units wherein the negative and positive components are at least retained together after image formation as the final print. The invention will accordingly be illustrated by reference to a typical film unit of this description.

As shown in the drawing, such a film unit may comprise, as the essential layers, a layer 13 of cyan dye developer, red-sensitive silver halide emulsion layer 14, interlayer 15, a layer of magenta dye developer 16, green-sensitive silver halide emulsion layer 17, interlayer 18, yellow dye developer layer 19, blue-sensitive silver halide emulsion layer 20, auxiliary layer 21, image-receiving layer or dyeable stratum 22, spacer layer 23, and a pH-reducing or neutralizing layer 24. Layers 1321 comprise the negative component and layers 22-24 comprise the positive component. These essential layers are shown to be confined between a dimensionally stable layer or support member 12 which is preferably opaque so as to permit development in the light and dimensionally stable layer or support member 25 which is effectively transparent to permit viewing of a color transfer image formed as a function of development in receiving layer or dyeable stratum 22. In accordance with this invention, the neutralizing layer is applied to a substrate comprising or containing the required cross-linking agent. In the embodiment shown in the drawing, this substrate is shown as sub-coat 25a on transparent support 25.

Layers l2 and 25 are preferably dimensionally stable liquid-impermeable layers which when taken together may possess a processing composition solvent vapor permeability sufficient to effect, subsequent to substantial transfer image formation and prior to any substantial environmental image degradation to which the resulting image may be prone, osmotic transpiration of processing composition solvent in a quantity effective to decrease the solvent from a first concentration at which the color-providing material is diffusible to a second concentration at which it is not. Although these layers may possess a vapor transmission rate of l or less gms./24 hrs/100 in. /mil., they preferably possess a vapor transmission rate for the processing composition solvent averaging not less than about 100 gms./24 hrs./ 100 inf/mil, most preferably in terms of the preferred solvent, water, a vapor transmission rate averaging in excess of about 300 gms. of water/24 hrs./l in. /mil., and may advantageously comprise a microporous polymeric film possessing a pore distribution which does not unduly interfere with the dimensional stability of the layers or, where required, the optical characteristics of such layers. As examples of useful materials of this nature, mention may be made of those having the aforementioned characteristics and which are derived from ethylene glycol terephthalic acid; vinyl chloride polymers; polyvinyl acetate; cellulose derivatives, etc. As heretofore noted layer 12 is of sufficient opacity to prevent fogging from occurring by light passing therethrough, and layer 26 is transparent to permit photoexposure and for viewing of a transfer image formed on receiving layer 23.

The silver halide layers preferably comprise photosensitive silver halide, e.g., silver chloride, bromide or iodide or mixed silver halides such as silver iodobromide or chloriodobromide dispersed in a suitable colloidal binder such as gelatin and such layers may typically be on the order of 0.6 to 6 microns in thickness.

It will be appreciated that the silver halide layers may and in fact generally do contain other adjuncts, e.g., chemical sensitizers 9 such as are disclosed in U. S. Pat. Nos. 1,574,944; 1,623,499; 2,410,689; 2,597,856; 2,597,915; 2,487,850; 2,518,698; 2,521,926; etc.; as well as other additives performing specific desired functions, e.g., coating aids, hardeners, viscosityincreasing agents, stabilizers, preservatives, ultraviolet absorbers and/or speed-increasing compounds. While the preferred binder for the silver halide is gelatin, others such as albumin, casein, zein, resins such as cellulose derivatives, polyacrylamides, vinyl polymers, etc., may replace the gelatin in whole or in part.

The respective dye developers, which may be any of those heretofore known in the art and disclosed for example in U.S. Pat. No. 2,983,606, etc., are preferably dispersed in an aqueous alkaline permeable polymeric binder, e.g., gelatin as a layer from about 1 to'7 microns in thickness.

lnterlayers 15, 18 and 21 may comprise an alkaline permeable polymeric material such as gelatin and may be on the order of from about 1 to 5 microns in thickness. As examples of other materials for forming these interlayers, mention may be made of thosedisclosed in U.S. Pat. Nos. 3,421,892, 3,575,701, 3,615,422 and 3,625,685. These interlayers may also contain additional reagents performing specific functions and the various ingredients necessary for development may also be contained initially in such layers in lieu of being present initially in the processing composition, in which event the desired developing composition is obtained by contacting such layers with the solvent for forming the processing composition, which solvent may include the other necessary ingredients dissolved therein.

The image-receiving layer may be on the order of 0.25 to 0.4 mil. in thickness. Typical materials heretofore employed for this layer include dyeable polymers such as nylon, e.g., N-methoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without placticizers; cellulose acetate with filler as, for example, onehalf cellulose acetate and one-half oleic acid; gelatin; polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, etc. Such receiving layers may, if desired, contain suitable mordants, e.g., any of the conventional mordant materials for acid dyes such as those disclosed, for example, in the aforementioned U.S. Pat. No. 3,227,550; as well as other additives such as ultraviolet absorbers, pH-reducing substances, etc. It may also contain specific reagents performing desired functions, e.g., a development restrainer, as disclosed, for example, in U.S. Pat. No. 3,265,498.

The spacer or timing layer may be on the order of 0.1 to 0.7 mil. thick. Materials heretofore used for this purpose include polymers which exhibit inverse temperature-dependent permeability to alkali, e. g., as disclosed in U.S. Pat. No. 3,445,686. Materials previously employed for this layer include polyvinyl alcohol, cyanoethylated polyvinyl alcohol, hydroxypropyl polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyvinyl oxazolidinone, hydroxypropyl methyl cellulose, partial acetals of polyvinyl alcohol such as partial polyvinyl butyral and partial polyvinyl propional, polyvinyl amides such as polyacrylamide, etc. One preferred timing layer comprises a graft polymer of the type described in U.S. Pat. No. 3,575,701.

The neutralizing layer may be on the order of 0.3 to 1.5 mil. in thickness. In accordance with this invention, it will comprise a cross-linkable acidic polymer, as previously discussed, the neutralizing layer being obtained by coating an aqueous solution of the acidic polymer by known coating techniques onto sub-coat a of transparent sheet material 25. The neutralizing layer will preferably contain less than 2,000 mgs. of solids per square foot of surface area. It may also contain other reagents performing specific desired functions, e.g., stabilizers, small amounts of a cross-linking agent such as gelatin, UV absorbers, etc.

Sub-coat 25a may be prepared by coating a surface of sheet 25 by known techniques to provide a very thin layer (e.g., on the order of 1 mil. or less) containing the desired cross-linking agent. By way of example, it may be prepared by coating a thin layer of gelatin on a surface of sheet 25.

By way of further illustrating the practice of this invention and the types of film units to which it is directed, an integral negative-positive film unit of the type described and claimed in U.S. Pat. No. 3,415,644 and shown in the illustrative drawing may be prepared, for example, by coating, in succession, on a gelatin subbed, 4 mil. opaque polyethylene terephthalate film base, the following layers:

1. a layer of cyan dye developer dispersed in gelatin and coated at a coverage of about 100 mgs./ft. of dye and about 80 mgs./ft. of gelatin;

2. a red-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 140 mgs./ft. of silver and about 70 mgs./ft. of gelatin;

3. a layer of a 60-30-4-6 copolymer of butylacrylate, diacetone acrylamide, styrene and methacrylic acid and polyacrylamide coated at a coverage of about 150 mgs./ft. of the copolymer and about 5 mgs./ft. of polyacrylamide;

4. a layer of magenta dye developer dispersed in gelatin and coated at a coverage of about 100 mgs./ft. of dye and about 100 mgs./ft. of gelatin;

5. a green-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 100 mgs./ft. of silver and about 50 mgs./ft. of gelatin;

6. a layer containing the copolymer referred to above in layer 3 and polyacrylamide coated at a coverage of about 100 mgs./ft. of copolymer and about l2 mgs./ft. of polyacrylamide;

7. a layer of yellow dye developer dispersed in gelatin and coated at a coverage of about 70 mgs./ft. of dye and about 56 mgs./ft. of gelatin;

8. a blue-sensitive gelatino silver iodobromide emulsion layer including the auxiliary developer 4'- methylphenyl hydroquinone coated at a coverage of about 120 mgs./ft. of silver, about 60 mgs./ft. of gelatin and about mgs./ft. of auxiliary developer; and

9. a layer of gelatin coated at a coverage of about 50 mgs./ft. of gelatin.

The three dye developers employed above may be the following:

a magenta dye developer; and

\ or- H,0

Water weight, to provide a neutralizing layer containing about 1,300 mgs. of solids/ftF;

2. a timing layer containing about a 40:1 ratio of a 60-30-4-6 copolymer of butylacrylate, diacetone acrylamide, styrene and methacrylic acid and polyacrylamide at a coverage of about 500 mgs./ft. and;

3. a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of about 400 mgs./ft. and including about 20 mgs./ft. of a development restrainer, l-phenyl-S-mercaptotetrazole, to provide a polymeric imagereceiving layer containing development restrainer.

The two components may then be laminated together to provide the desired integral film unit.

A rupturable container comprising an outer layer of lead foil and an inner liner or layer of polyvinyl chloride retaining an aqueous alkaline processing solution may then be fixedly mounted on the leading edge of each of the laminates, by pressure-sensitive tapes, interconnecting the respective container and laminates so that, upon application of compressive pressure to the container to rupture the containers marginal seal, its contents may be distributed between the dyeable stratum (layer 3 of the positive component) and the gelatin layer (layer 9) of the negative component.

An illustrative processing composition to be employed in the rupturable container may comprise the following properties of ingredients:

100 cc. Potassium hydroxide 11.2 gins. Hydroxyethyl cellulose (high viscosity) [commercially 3.4 gins.

available from Hercules Powder 00., Wilmington, Delaware, under the trade name Natrasol 250].

N-phenethyl-a-picolinium bromide 2.7 gins.

Benzotriazole 1.15 gins.

Titanium dioxide 50.0 gins.

'fl 2.0a gms.

n- C uHgr- This film unit may then be exposed in known manner to form a developable image and the thus exposed element may then be developed by applying compressive pressure to the rupturable container in order to distribute the aqueous alkaline processing composition, thereby forming a multicolor transfer image which is viewable through the transparent polyethylene terephthalate film base as a positive reflection print.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a photographic product comprising a photosensitive element including at least one light-sensitive silver halide layer having a dye imageproviding material associated therewith or an imagereceiving element including a stratum adapted for receiving an image by diffusion transfer, said photographic product including a dimensionally stable support carrying a neutralizing layer for lowering the environmental pl-l subsequent to application of an aqueous alkaline processing composition;

the improvement wherein said neutralizing layer comprises a copolymer applied from an aqueous coating solution of a water-soluble, cross-linkable copolymer of a vinyl acid and a vinyl aldehyde; a layer between said support and said neutralizing layer and contiguous with said neutralizing layer and including a non-diffusible proteinaceous material which is a cross-linking agent for said'copolymer so that said copolymer is cross-linked at least at the interface between said neutralizing layer and said layer including said cross-linking agent.

2. A product as defined in claim 1 wherein said copolymer is a copolymer of a vinyl carboxylic acid and a vinyl carboxylic acid aldehyde.

3. A photographic product as defined 'in claim 1 wherein said layer including said cross-linking agent comprises a gelatino layer.

4. A photosensitive element including at least one light-sensitive silver halide layer having a dye imageproviding material associated therewith, a dimensionally stable support carrying a neutralizing layer prepared by coating an aqueous solution of a watersoluble, cross-linkable copolymer of a vinyl acid and a vinyl aldehyde and thereafter removing said aqueous solvent; and between said support and said neutralizing layer a contiguous layer including a non-diffusible, proteinaceous material which is a cross-linking agent for said copolymer, said copolymer being cross-linked and thereby hardened at least at the interface between said neutralizing layer and said contiguous layer.

5. A photosensitive element as defined in claim 4 including a dyeable stratum adapted for forming a color image by diffusion transfer.

6. A photosensitive element as defined in claim 5 wherein said dyeable stratum is disposed between said silver halide strata and associated dye image-providing material and said neutralizing layer.

7. A photosensitive element as defined in claim 4 wherein said copolymer comprises a copolymer of a vinyl carboxylic acid and a vinyl carboxylic acid aldehyde.

8. A photosensitive element as defined in claim 4 wherein said contiguous layer comprises a gelatincontaining layer.

9. A photosensitive element as defined in claim 4 wherein said neutralizing layer includes gelatin.

10. In an integral negative-positive film unit including a negative component comprising at least one lightsensitive silver halide emulsion layer having a dye image-providing material associated therewith, a positive component including at least a dyeable stratum, means for applying a reflecting layer between said positive and negative components in an amount sufficient upon development of said film unit to mask effectively said negative component and to provide a background for viewing a color image imparted to said dyeable stratum of said positive component by reflected light by applying an aqueous alkaline processing fluid to said film unit after exposure thereof, said film unit further including a dimensionally stable transparent support carrying a neutralizing layer for lowering the environmental pH subsequent to application of said alkaline processing fluid;

the improvement wherein said neutralizing layer comprises a water soluble, cross-linkable copolymer of a vinyl acid and a vinyl aldehyde applied from an aqueous coating solution of a watersoluble cross-linkable acidic polymer; and positioned between said neutralizing layer and said support is a layer contiguous with said neutralizing layer including a non-diffusible, proteinaceous material which is a cross-linking agent for said copolymer so that said water-soluble copolymer is crosslinked at least at the interface between said neutralizing layer and said layer including said crosslinking agent.

11. A film unit as defined in claim wherein said neutralizing layer is disposed on the side of said dyeable stratum opposed from said negative component.

12. A film unit as defined in claim 10 wherein a timing layer is disposed between said dyeable stratum and said neutralizing layer.

13. A film unit as defined in claim 10 wherein said negative component includes a red-sensitive silver halide emulsion having a cyan dye image-providing material associated therewith, a green-sensitive silver halide emulsion having a magenta dye image-providing material associated therewith and a blue-sensitive silver halide emulsion having a yellow dye image-providing material associated therewith.

14. A film unit as defined in claim 10 wherein said dye image-providing materials-are initially soluble or diffusible in said aqueous alkaline processing fluid but are selectively rendered non-diffusible in an imagewise pattern as a function of development.

15. A film unit as defined in claim 10 including means for applying said aqueous alkaline processing fluid to develop said film unit.

16. A film unit as defined in claim 10 wherein said negative and positive components are confined between a pair of support members, at least the support member associated with the positive component being transparent.

17. A film unit as defined in claim 10 wherein said positive and negative components are confined on a transparent support member associated with said positive component.

18. A film unit as defined in claim 10 wherein said means for applying a reflecting layer comprises a layer I of a white pigment disposed in a layer between said positive and negative components.

19. A film unit as defined in claim 10 wherein said means for applying a reflecting layer comprises a white pigment dispersed in said processing fluid.

20. A film unit as defined in claim 10 wherein said copolymer comprises a copolymer of vinyl carboxylic acid and a vinyl carboxylic acid aldehyde.

21. A film unit as defined in claim 20 wherein said neutralizing layer further contains a proteinaceous cross-linking agent.

22. A photosensitive element including a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer, a layer containing a cyan dye developer, a red-sensitive gelatino silver halide emulsion layer, a layer containing a magenta dye developer, a greensensitive gelatino silver halide emulsion layer, a layer containing a yellow dye developer, a blue-sensitive gelatino silver halide emulsion layer, a dyeable stratum, a neutralizing layer comprising a cross-linkable copolymer of a vinyl acid and a vinyl aldehyde which is watersoluble in its noncross-linked form, said copolymer providing acid in an amount sufficient to effect reduction of a processing solution having a first pH at which said dye developers are soluble and diffusible to a second pH at which said dye developers are substantially insoluble and non-diffusible, a layer including a proteinaceous material which is cross-linking agent for said copolymer, said copolymer in said neutralizing layer being cross-linked at least at the interface between said neutralizing layer and said layer including said cross-linking agent, a dimensionally stable alkaline solution impermeable transparent layer, means securing at least the side edges of said opposed layers in fixed relationship, and a rupturable container retaining an aqueous alkaline processing solution having said first pH and containing dispersed therein a white inorganic pigment in a quantity sufficient to mask effectively said silver halide layers and any dye developer associated therewith after development and to provide a background for viewing a diffusion transfer image formed l by development of said film unit, by reflected light,

through said transparent layer, said rupturable container being fixedly positioned and extending transverse a leading edge of said photosensitive element so as to be capable of effecting unidirectional discharge of the containers contents between said dyeable stratum and said blue-sensitive emulsion layer upon application of compressive force to said container.

23. A photosensitive element as defined in claim 22 wherein said water-soluble acidic polymer comprises a copolymer of a vinyl carboxylic acid and a vinyl carboxylic acid aldehyde.

24. A film unit as defined in claim 23 wherein the ratio of vinyl acid to vinyl aldehyde is at least 85:15.

25. A film unit as defined in claim 23 wherein said neutralizing layer also includes gelatin.

26. A film unit as defined in claim 24 wherein said layer including said cross-linking agent comprises a gelatincontaining layer.

27. A film unit as defined in claim 22 wherein said cyan dye developer is a phthalocyanine dye developer; said magenta dye developer is a 1:1 chrome-complexed azo dye developer; and said yellow dye developer is a 1:1 chromecomplexed azomethine dye developer.

28. A film unit as defined in claim 27 including a timing layer disposed between said dyeable stratum and said neutralizing layer.

29. A process for forming a visible image in color comprising the steps of exposing a photosensitive element as defined in claim 5 to form a developable image and thereafter applying an aqueous alkaline processing composition to said exposed element to form said color image.

30. A process for forming a color transfer image comprising the steps of exposing a film unit as defined in claim 10 to form a developable image and thereafter applying an aqueous alkaline processing composition to develop said image and toform, as a function of development, an imagewise distribution of dye imageproviding material which is transferred, at least in part, by diffusion, to said dyeable stratum to impart thereto a color transfer image viewable, without separation, by

reflected light as a positive color reflection print. 

2. A product as defined in claim 1 wherein said copolymer is a copolymer of a vinyl carboxylic acid and a vinyl carboxylic acid aldehyde.
 3. A photographic product as defined in claim 1 wherein said layer including said cross-linking agent comprises a gelatino layer.
 4. A photosensitive element including at least one light-sensitive silver halide layer having a dye image-providing material associated therewith, a dimensionally stable support carrying a neutralizing layer prepared by coating an aqueous solution of a water-soluble, cross-linkable copolymer of a vinyl acid and a vinyl aldehyde and thereafter removing said aqueous solvent; and between said support and said neutralizing layer a contiguous layer including a non-diffusible, proteinaceous material which is a cross-linking agent for said copolymer, said copolymer being cross-linked and thereby hardened at least at the interface between said neutralizing layer and said contiguous layer.
 5. A photosensitive element as defined in claim 4 including a dyeable stratum adapted for forming a color image by diffusion transfer.
 6. A photosensitive element as defined in claim 5 wherein said dyeable stratum is disposed between said silver halide strata and associated dye image-providing material and said neutralizing layer.
 7. A photosensitive element as defined in claim 4 wherein said copolymer comprises a copolymer of a vinyl carboxylic acid and a vinyl carboxylic acid aldehyde.
 8. A photosensitive element as defined in claim 4 wherein said contiguous layer comprises a gelatin-containing layer.
 9. A photosensitive element as defined in claim 4 wherein said neutralizing layer includes gelatin.
 10. In an integral negative-positive film unit including a negative component comprising at least one light-sensitive silver halide emulsion layer having a dye image-providing material associated therewith, a positive component including at least a dyeable stratum, means for applying a reflecting layer between said positive and negative components in an amount sufficient upon development of said film unit to mask effectively said negative component and to provide a background for viewing a color image imparted to said dyeable stratum of said positive component by reflected light by applying an aqueous alkaline processing fluid to said film unit after exposure thereof, said film unit further including a dimensionally stable transparent support carrying a neutralizing layer for lowering the environmental pH subsequent to application of said alkaline processing fluid; the improvement wherein said neutralizing layer comprises a water soluble, cross-linkable copolymer of a vinyl acid and a vinyl aldehyde applied from an aqueous coating solution of a water-soluble cross-linkable acidic polymer; and positioned between said neutralizing layer and said support is a layer contiguous with said neutralizing layer including a non-diffusible, proteinaceous material which is a cross-linking agent for said copolymer so that said water-soluble copolymer is cross-linked at least at the interface between said neutralizing layer and said layer including said cross-linking agent.
 11. A film unit as defined in claim 10 wherein said neutralizing layer is disposed on the side of said dyeable stratum opposed from said negative component.
 12. A film unit as defined in claim 10 wherein a timing layer is disposed between said dyeable stratum and said neutralizing layer.
 13. A film unit as defined in claim 10 wherein said negative component includes a red-sensitive silver halide emulsion having a cyan dye image-providing material associated therewith, a green-sensitive silver halide emulsion having a magenta dye image-providing material associated therewith and a blue-sensitive silver halide emulsion having a yellow dye image-providing material associated therewith.
 14. A film Unit as defined in claim 10 wherein said dye image-providing materials are initially soluble or diffusible in said aqueous alkaline processing fluid but are selectively rendered non-diffusible in an imagewise pattern as a function of development.
 15. A film unit as defined in claim 10 including means for applying said aqueous alkaline processing fluid to develop said film unit.
 16. A film unit as defined in claim 10 wherein said negative and positive components are confined between a pair of support members, at least the support member associated with the positive component being transparent.
 17. A film unit as defined in claim 10 wherein said positive and negative components are confined on a transparent support member associated with said positive component.
 18. A film unit as defined in claim 10 wherein said means for applying a reflecting layer comprises a layer of a white pigment disposed in a layer between said positive and negative components.
 19. A film unit as defined in claim 10 wherein said means for applying a reflecting layer comprises a white pigment dispersed in said processing fluid.
 20. A film unit as defined in claim 10 wherein said copolymer comprises a copolymer of vinyl carboxylic acid and a vinyl carboxylic acid aldehyde.
 21. A film unit as defined in claim 20 wherein said neutralizing layer further contains a proteinaceous cross-linking agent.
 22. A photosensitive element including a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer, a layer containing a cyan dye developer, a red-sensitive gelatino silver halide emulsion layer, a layer containing a magenta dye developer, a green-sensitive gelatino silver halide emulsion layer, a layer containing a yellow dye developer, a blue-sensitive gelatino silver halide emulsion layer, a dyeable stratum, a neutralizing layer comprising a cross-linkable copolymer of a vinyl acid and a vinyl aldehyde which is water-soluble in its noncross-linked form, said copolymer providing acid in an amount sufficient to effect reduction of a processing solution having a first pH at which said dye developers are soluble and diffusible to a second pH at which said dye developers are substantially insoluble and non-diffusible, a layer including a proteinaceous material which is cross-linking agent for said copolymer, said copolymer in said neutralizing layer being cross-linked at least at the interface between said neutralizing layer and said layer including said cross-linking agent, a dimensionally stable alkaline solution impermeable transparent layer, means securing at least the side edges of said opposed layers in fixed relationship, and a rupturable container retaining an aqueous alkaline processing solution having said first pH and containing dispersed therein a white inorganic pigment in a quantity sufficient to mask effectively said silver halide layers and any dye developer associated therewith after development and to provide a background for viewing a diffusion transfer image formed by development of said film unit, by reflected light, through said transparent layer, said rupturable container being fixedly positioned and extending transverse a leading edge of said photosensitive element so as to be capable of effecting unidirectional discharge of the container''s contents between said dyeable stratum and said blue-sensitive emulsion layer upon application of compressive force to said container.
 23. A photosensitive element as defined in claim 22 wherein said water-soluble acidic polymer comprises a copolymer of a vinyl carboxylic acid and a vinyl carboxylic acid aldehyde.
 24. A film unit as defined in claim 23 wherein the ratio of vinyl acid to vinyl aldehyde is at least 85:15.
 25. A film unit as defined in claim 23 wherein said neutralizing layer also includes gelatin.
 26. A film unit as defined in claim 24 wherein said layer including said cross-linking agent comprises a gelatincontainiNg layer.
 27. A film unit as defined in claim 22 wherein said cyan dye developer is a phthalocyanine dye developer; said magenta dye developer is a 1:1 chrome-complexed azo dye developer; and said yellow dye developer is a 1:1 chromecomplexed azomethine dye developer.
 28. A film unit as defined in claim 27 including a timing layer disposed between said dyeable stratum and said neutralizing layer.
 29. A process for forming a visible image in color comprising the steps of exposing a photosensitive element as defined in claim 5 to form a developable image and thereafter applying an aqueous alkaline processing composition to said exposed element to form said color image.
 30. A process for forming a color transfer image comprising the steps of exposing a film unit as defined in claim 10 to form a developable image and thereafter applying an aqueous alkaline processing composition to develop said image and to form, as a function of development, an imagewise distribution of dye image-providing material which is transferred, at least in part, by diffusion, to said dyeable stratum to impart thereto a color transfer image viewable, without separation, by reflected light as a positive color reflection print. 